During the past year the same animal model was utilized for cerebral flow studies. Under local anesthesia and a tranquilizer a maternal celiotomy is done. A catheter is placed in the fetal femoral artery and vein. A catheter is placed in a tributory of the jugular vein and then threaded into the vein. A cuff-type flow probe in placed around the carotid artery and EKG electrodes placed in the scapular areas. The mother is then allowed to recover for 24 hr. Baseline blood samples are taken from the maternal femoral artery and fetal artery and vein to be analyzed for PO2, PCO2, pH and base excess. An injection of chromium labelled microspheres is then given to the fetus via the fetal femoral vein. The mother is given a 10% oxygen mixture to breathe for 3-5 minutes. At about 3 min of low oxygen a second injection of microspheres cerium is given to the fetus through the femoral vein. Five successful low oxygen studies were carried out. We intend to increase these numbers during the coming year. We have also looked at the relationship between the fetal coronary flow and the preejection period of the heart during the past year. There is a definite relationship between fetal age and fetal pH with systolic time interval. This too will be further investigated during the coming year. BIBLIOGRAPHIC REFERENCE: Ikenoue, T., Quilligan, E.J. and Murata, Y.: Circulatory response to atropine in sheep fetus. Amer. J. Obstet. & Gynec. 126:253-260, Sept. 15, 1976.